In order to prevent external fields from entering into the areas in need of protection in an electronic device, it is usually required to protect the electronic device using shielding technology. Currently, various shielding methods have been developed to protect the electronic device against damage from external electrostatic discharge. The active overlay technology used for electrostatic discharge shielding mainly aims at the research on shielding materials and shielding layers based on a flexible printed circuit board. For example, the Chinese application for a patent for invention under publication number CN101267706A discloses a technical solution as to electrostatic discharge shielding materials in which an anti-electrostatic shielding sheet with a multi-layer structure is designed, including various combined design schemes of anti-electrostatic layer, shielding layer, and filling layer. In addition, the Chinese application for a patent for invention under the publication number CN101287328A discloses a technical solution of a flexible printed circuit board which combines shielding function, wherein the internal of the flexible printed circuit board is provided with a grounding electrostatic shield to provide stable anti-electromagnetic interference protection for the placement section of electronic elements.
However, the design of the multi-layer structure or the design of the flexible printed circuit board which combines shielding function still has deficiencies. For example, in the case of the design of the multi-layer structure, said multi-layer structure almost completely covers the external of the electronic device, but it is unconsidered which areas are required to be covered, this causes waste in the manufacture cost. In addition, due to attached components on the flexible printed circuit board, when these components are covered by the multi-layer structure, the thickness of the whole active overlay is uneven, in particular, the places of these components where are covered by the multi-layer structure would be higher than other positions, this brings difficulties to flatness control of the whole active overlay. Moreover, in the case of the design of the flexible printed circuit board that combines shielding function, there also exists the problem of waste in the manufacture cost.
In order to reduce the manufacture cost, those skilled in the art conceived of using net active overlay to replace the original design concept of completely covering the external surface of the electronic device, namely making a hole in the active overlay at corresponding positions of the electronic components not in need of protection, in this way the corresponding electronic components are not covered by the active overlay, thereby reducing the manufacture cost and relieving the deficiencies that the active overlay near the electronic components is too thick and the flatness is too poor. However, this also leads to risks that the electronic components in need of protection are not protected by the electrostatic shielding. Moreover, there is interference between the net active overlay and attached electronic components, for example if an LED is covered by the net active overlay, the net active overlay may cause uneven shadow present in the transmission light.
Consequently, there is an urgent need to improve the electrostatic shielding technology in the art.